In March 1986 Dye Arup Transportation Planning was commissioned by the Department of Main Roads (DMR) to collect, assemble and collate traffic information to assist the DMR to analyse and make decisions regarding the completion of the missing link on the Western Freeway F4. This section is between Mays Hill and Prospect, 25 to 35 kilo- metres to the west of Sydney. Of particular importance is the section between 30 and 35 km where several alternative solutions are to be assessed. The study area and its regional context are shown in Figure 1. Information held by the DMR was reviewed and surveys undertaken by the consultants and contractors in March and April 1986. This Working Paper presents a summary of the traffic pattern within the study area and is based on traffic data surveyed between 1980 and 1986.